1-substituted-2-indoline hydrazone photoconductors

ABSTRACT

1-Substituted-2-indoline hydrazones are useful as photoconductors.

United States Patent [191 Shea [ l-SUBSTITUTED-Z-INDOLINE HYDRAZONE I PHOTOCONDUCTORS [75] Inventor: Michael D. Shea, Rochester, NY.

[73] Assignee: Eastman Kodak Company,

Rochester, N .Y.

22 Filed: July 6,1971

21 App1.No.: 160,064

[56] References Cited UNITED STATES PATENTS 3,417,082 12/1968 Taylor ..260/240G 1 Oct. 16, 1973 2,872,449 2/1959 Baumann et a1 260/240 G 3,499,902 3/1970 Coles et a1. 260/240 G 3,149,990 9/1964 Coles et a1. 260/240 G 3,290,147 12/1966 Matter et a] 96/1.5 3,230,081 1/1966 Tomanek et a1 96/l.5

FOREIGN PATENTS OR APPLICATIONS 641,983 5/1962 Canada 96/1 PC Primary Examiner-Roland E. Martin, Jr. Att0rneyRobe11 W. Hampton et a1.

[ 7] ABSTRACT 1-Subst iti1ted-2-indo1ine hydrazones are useful as photoconductors.

6 Claims, No Drawings l-SUBSTlTUTED-2-INDOLINE HYDRAZONE PHOTOCONDUCTORS This invention relates to electrophotography and more particularly to a novel class of photoconductive materials and compositions and elements produced therefrom.

Electrophotographic processes employ an electrophotographic or photoconductive element comprising a coating of a photoconductive insulating material on a conductive support. The element is given a uniform surface charge in the dark and then is exposed to an image pattern of activating electromagnetic radiation such as light or x-rays. The charge on the photoconductive element is dissipated in the illuminated area to form an electrostatic charge pattern which is then developed by contact with an electroscopic marking material. The marking material or toner, as it is also called, whether carried in an insulating liquid or in the form of a dry powder, deposits on the exposed surface in accordance with either the charge pattern or the discharge pattern, as desired. Then, if the photoconductive element is of the non-reusable type, the developed image is fixed by fusion or other means to the surface of the photoconductive element. If the element is of the reusable type, e.g., a selenium-coated drum, the image is transferred to another surface such as paper and then recent works such as Electrophotography by R. M.

Schaffert, published by Focal Press Ltd., 1965.

The photoconductive compounds that have been used in electrophotographic processes have included both organic and inorganiccompounds. The organic photoconductors have been desirable for a number of reasons. For instance, the organics are less abrasive than the inorganics. They can be charged to high'negative or positive potential while the inorganics often saturate at low potential and accept only a positive or a negative charge. In addition, the organics usually offer greater exposure latitude, can be spectrally sensitized more effectively and offer a number of other advantages over zinc oxide and other inorganics;

However, the selection of photoconductive com-' pounds for incorporation into electrophotographic.

compositions has .proceeded on a compound-bycompound basis. Nothing as yet has been discovered from the large number of difi'erent photoconductive substances tested which permits effective prediction and, therefore, selection of which compounds will exhibit desirable electrophotographic properties.

It is, therefore, an object of this invention to provide a novel class of photoconductive compounds.

It is another object of this invention to provide a novel class of photoconductors having high photosensiuseful electrophotographic speeds.

It is a further object of this invention to provide an improved process utilizing the novel photoconductors described herein.

These and other objects are accomplished by employing l-substituted-Z-indoline hydrazones as photoconductors. These materials can be substituted in various positions by any one or more of several substituents. Typically, the phenyl nucleus can be substituted with lower alkyl, aryl, halogen, alkoxy, aryloxy, amino or cyano groups, the nitrogen of the indole nucleus can be substituted with lower alkyl or aryl, and the terminal carbon atom can similarly be substituted with lower alkyl or aryl, all as hereinafter set forth with greater particularity.

The 2-indoline hydrazones having utility according to the present invention are those corresponding to the following'formula:

R,, R and R; can be the same or different substituv ents each representing any of the following:

1. an alkyl radical having one to eight carbon atoms e.g., methyl, ethyl, propyl, butyl, isobutyl, octyl, etc, including a substituted alkyl group having one to eight carbon atoms such as a. alko'xyalkyl, e.g., ethoxypropyl, methoxybutyl,

propoxymethyl, etc,

b. aryloxyalkyl, e.g., phenoxyethyl,

ymethyl, phenoxypentyl, etc,

0. aminoalkyl, e.g., aminobutyl, aminoethyl, aminopropyl, etc,

naphthoxd. hydroxyalkyl, e.g., hydroxypropyl, hydroxyoctyl,

etc, e. aralkyl, e.g., benzyl, phenethyl, etc, f. alkylaminoalkyl, e.g., methylaminopropyl, me-

thylaminoethyl, etc, and also including dialkyldimevwherein R is hydroxy, h;dro g eii, aryl, e.g., phenyl,

naphthyl, etc., lower alkyl having one to eight carbon atoms, e.g., methyl, ethyl, propyl, etc, amino, including substituted amino,'e.g., diloweralkylamino, lower alkoxy having one to eight carbon atoms, e.g., butoxy, methoxy, etc, aryloxy, e.g., phenoxy, naphthoxy, etc;

2. an aryl group, e.g., phenyl, naphthyl, nathryl, fluorenyl, etc, including a substituted aryl group such as a. alkoxyaryl, e.g., ethoxyphenyl, methoxyphenyl, propoxynaphthyl, etc,

b. aryloxyaryl, e.g., phenoxyphenyl, naphthoxyphenyl, phenoxynaphthyl, etc,

c, aminoaryl, e.g., aminophenyl, aminonaphthyl,

aminoanthryl, etc,

may in turn carry substituents such as those set forth hereinbefore.

X is an oxygen atom, a sulfur atom, a selenium atom, an imino group including a substituted imino group, or a methylene group including a substituted methylene group.

d. hydroxyaryl, e.g., hydroxyphenyl, hydroxynaphthyl, hydroxyanthryl, etc, e. biphenylyl, f. alkylaminoaryl, e.g., methylaminophenyl, me-

thylaminonaphthyl etc, and also including dialkylaminoaryl, e.g., diethylaminophenyl, di-

propylaminophenyl, etc,

g. arylaminoaryl, e,g., phenylaminophenyl, diphenylaminophenyl, N-phenyl-N- ethylaminophenyl, naphthylaminophenyl, etc,

h. nitroaryl, e.g., nitrophenyl,nitronaphthyl, nitroanthryl, etc,

i. cyanoaryl, e.g, cyanophenyl, cyanonaphthyl, cyanoanthryl, etc,

j. haloaryl, e.g., chlorophenyl, bromophenyl, chloronaphthyl, etc,

k. aryl substituted with an acyl group having the formula ALB wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc, amino, including substituted amino, e;g., diloweralkylamino, lower alkoxy having one to eight carbon atoms, e.g., butoxy, methoxy, etc, aryloxy, e.g., phe'noxy, naphthoxy, etc, lower alkyl having one to eight carbon atoms, e.g., methyl, ethyl, propyl, butyl,

etc,

l. alkanyl, e.g., tolyl, ethylphenyl, propyl, naphthyl,.-

etc,

3. hydrogen:

R R R and R, each represents any of the substituents set forth above for R R and R and also can be any-of the following:

1. an alkoxy group having 1 to 8 carbon atoms, e.g.,

, methoxy, ethoxy, propoxy, butoxy, etc;

2. an aryloxy group, e.g., phenoxy, naphthoxy, etc;

3. halogen, e.g;, chlorine, fluorine, bromine or iodine; i

4. amino having the formula wherein ,R and R" are the same or different including hydrogen, lower alkyl having one to eight carbon atoms 'such as ethyl, propyl, butyl, etc, aryl such as phenyl,

naphthyl, etc, halogen, e.g., chlorine, bromine, etc,

5. cyano; or

any of R R R and R may be taken with an adjacent substituent to represent the number of atoms to complete a fused carbocyclic or heterocyclic ring system containing up to about 19 carbon atoms, which Preferred photoconductors of the invention ar those corresponding to the formula:

R R and R each represents a hydrogen atom, a lower alkyl radical having from 1 to about 4 carbon atoms, e.g., methyl, ethyl, isopropyl, tert-butyl, etc, or an aryl radical including a substituted aryl radical, preferably an amino-substituted aryl radical;

and

Y is an oxygen atom, a sulfur atom or an imino radical.

Particularly preferred photoconductors of the invention are those represented by the formula:

. wherein:

R -is a lower alkyl radical having from 1 to about 4 carbon atoms such as those set forth for R R and R above, and

R is a phenyl radical including a substituted phenyl radical, such as an amino-substituted phenyl radical including dialkylaminoand diarylaminosubstituted phenyl radicals, or a naphthyl radical.

Typical compounds which belong to the herein described general class of photoconductive materials include the following listed in Table 1 below.

TABLE 1 graphic properties when compared to those photoconductors described in the prior art. These enhanced properties are observed when the elements accept a suitable surface potential (e.g., 500-600 volts) and are subsequently exposed to actinic radiation. The relative electrophotographic speed of the element is determined on the basis of the reciprocal of the exposure required to reduce the potential of the surface charge by 100 volts (shoulder speed) or to 100 volts (toe speed). The terms shoulder speed and toe speed are terms known in the photographic art with reference to H and D curves. As used herein, such terms refer to corresponding curves resulting from exposure plotted against voltage. The reduction of the surface potential to 100 volts or below is significant in that is represents a requirement for suitable broad area development of an electrostatic image. The relative speed at 100 volts is a measure of the ability to produce and hence, to develop or otherwise utilize the electrostatic image.

' When many conventional photoconductors are used,

the surface potential frequently does not drop to or below 100 volts and, therefore, no toe speed can be assigned to such a composition. The photoconductive compositions disclosed herein do exhibit useful toe speeds.

Electrophotographic elements of the invention can be prepared with the photoconducting compounds of the invention in the usual manner, i.e., by blending a dispersion or solution of a photoconductive compound together with a binder, when necessary or desirable, and coating or forming a self-supporting layer with the photoconductor-containing materials. Mixtures of the photoconductors described herein can be employed. In addition, supplemental materials useful for changing the spectral sensitivity or electrophotosensitivity of the element can be added to the composition of the'element when it is desirable to produce the characteristic effect of such materials.

The photoconductive layers of the invention can also be sensitized by the addition of effective amounts of sensitizing compounds to exhibit improvedelectrophotosensitivity. Sensitizing compounds useful with the photoconductive compounds of the present invention can be selected from a wide variety of materials, including such materials as pyrylium dye salts, including thiapyrylium dye salts and selenapyrylium dye salts disclosed in VanAllan et al, U.S. Pat. No. 3,250,615, issued May 10, 1966; hexaphenyl-p-rosaniline; fluorenes, such as 7,12-dioxo-l3dibenzo(a,h)fluorene, 5,- 10-dioxo-4a,ll-diazobenzo(b)fluorene, 3,13-dioxo-7- oxadibenzo(b,g)fluorene, and the like; aggregate-type sensitizers of the type described in Light, British Patent No. 1,153,506, dated May 29, 1969; aromatic nitro compounds of the kinds described in Minsk U.S. Pat. No. 2,610,120, dated Sept. 9, 1952; anthrones like those disclosed in Zvanut U.S. Pat. No. 2,670,284, dated Feb. 23, 1954; quinones as those in Minsk U.S. Pat. No. 2, 670,286, dated Feb. 23, 1954; benzophenones as those in Minsk U.S. Pat. No. 2,260,287, dated Feb. 23, 1954; thiazoles as those of Robertson U.S. Pat. No. 2,732,301, dated Jan. 24, 1956; mineral acids, carboxylic acids, such as maleic acid, dichloroacetic acid, trichloroacetic acid and salicylic acid; sulfonic and phosphoric acids; and various dyes, such as cyanine (including carbocyanine and polycarbocyanine), merocyanine, diarylmethane, thiazine, azine, oxazine, xanthene, phthalein, acridine, azo, anthraquinone dyes andthe like and mixtures thereof. The sensitizers preferred for use with thecompounds of this invention are selected from pyrylium salts including selenpyrylium salts and thiapyrylium salts, and cyanine dyes including carboxyanine dyes.

Where a sensitizing compound is employed with the binder and organic photoconductor to form a sensitized electrophotographic element, it is the normal practice to mix a suitable amount of the sensitizing compound with the coating composition so that, after thorough mixing, the sensitizing compound is uniformly distributed in the coated layer.

Other methods of incorporating the sensitizer or the effect of the sensitizer may, however, be employed consistent with the practice of this invention. In preparing the photoconductive layers, no sensitizing compound is requried to give photoconductivity in the layers which contain the photoconducting substances; therefore, no sensitizer is required in a particuiar photoconductive layer. However, since relatively minor amounts of sensititizing compound give substantial improvement in speed in such layers, the sensitizer is preferred. The amount of sensitizer that can be added to a photoconductor-incorporating layer to give effective increases in speed can vary widely. The optimum concentration in any given case will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.0001 to about 30 percent by weight based on the weight of the film-forming coating composition. Normally, a sensitizer is added to the coating composition in an amount by weight from about 0.001 to about 30 percent and preferably about 0.005 to about 5.0 percent by weight of the total coating composition.

Preferred binders for use in preparing the present photoconductive layers are film-forming, polymeric binders having fairly high dielectric strength which are good electrically insulating film-forming vehicles.

Typical of these materials are:

I. Natural resins including gelatin, cellulose ester derivatives such as alkyl esters of carboxylate d cellulose, hydroxyethyl, cellulose, carboxy methyl cellulose, carboxy methyl hydroxy ethyl cellulose, etc;

II. Vinyl resins including:

a. polyvinyl esters such as a vinyl acetate resin, a copolymer of vinyl acetate and crotonic acid, a copolymer of vinyl acetate with an ester of vinyl alcohol and a higher aliphatic carbox'ylic acid such as aluric acid or stearic acid, polyvinyl stearate, a copolymer of vinyl acetate and maleic acid, a poly(- vinylhaloarylate) such as poly(vinyl-m-bromobenzoate-co-vinyl acetate), a terpolymer of vinyl butyral with vinyl alcohol and vinyl acetate, etc;

b. vinyl chloride and vinylidene chloride polymers such as a poly(vinylchloride), a copolymer of vinyl chloride and vinyl isobutyl ether, a copolymer of vinylidene chloride with acrylonitrile or vinyl chloride, a terpolymer of vinyl chloride, vinyl acetate and vinyl alcohol, poly(vinylidene chloride) a terpolymer of vinyl chloride, vinyl acetate and maleic anhydride, a copolymer of vinyl chloride and vinyl acetate, etc;

0. styrene .polymers such as polystyrene, a nitrated polystyrene, a copolymer of styrene and minoisobutyl maleate, a copolymer of styrene acid polyvinyltoluene, a copolymer of styrene with methacrylic acid, a copolymer of styrene and butadiene, a copolymer of dimethylitaconate and styrene, polymethylstyrene, etc;

d. methacrylic acid ester polymers such as a poly-alkylmethacrylate), etc;

2. polyolefins such as chlorinated polyethylene, chlorinated polypropylene, poly(isobutylene), etc;

f. poly(vinyl acetals) such as poly(vinyl butyral), etc;

and

g. poly(vinyl alcohol);

lll. Polycondensates including:

a. a polyester of 1,3-disulfobenzene and 2,2-bis-(4- hydroxyphenyl)propane;

b. a polyester of diphenyl-p,p-disulfonic acid and 2,-

2-bis(4-hydroxyphenyl)propane;

c. a polyester of 4,4'-dicarboxyphenyl ether and 2,2-

bis(4-hydroxyphenyl)propane;

d. a polyester of 2,2-bis(4-hydroxyphenyl)propane and fumaric acid;

e. polyester of pentaerythritol and phthalic acid;

f. resinous terpene polybasic acid;

g. a polyesterof phosphoric acid and hydroquinone;

h. polyphosphites;

i. polyester of neopentylglycol and isophthalic acid;

j. polycarbonates including polythiocarbonates such as the polycarbonate of 2,2-bis(4-hydroxyphenyl)- propane;

k. polyester of isophthalic acid, 2,2-bis[4-(B- hydroxyethoxy)phenyl]propane and ethylene glycol;

l. polyester of terephthalic acid, 2,2-bis([4-(fihydroxyethoxy)phenyl]propane and ethylene glyco];

m. polyester of ethylene, glycol, neopentyl, glycol,

terephthalic acid and isophthalic acid;

n. polyamides;

0. ketone resins; and

p. phenolformaldehyde resins;

lV. Silicone resins;

V. Alkyd resins including styrene-alkyd resins, silicone-alkyd resins, soya-alkyd resins, etc;

Vl. Paraffin; and

VII. Mineral waxes.

Solvents useful for preparing coating compositions with the'photo'conductors of the present invention can include a wide variety of organic solvents for the components of the coating composition.

Typical solvents include:

1. aromatic hydrocarbons such as benzene, naphthalene, etc, including substituted aromatic hydrocarbons such as toluene, xylene, methylene, etc;

'2. ketones such as acetone, Z-butanone, etc;

3. halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, ethylene chloride, etc;

4. ethers including cyclic ethers such as tetrahydrofuran, ethylether;

5. mixtures of the above.

In preparing the coating compositions utilizing the photoconducting compounds disclosed herein, useful results are obtained where the photoconductive substance is present in an amount equal to at least about 1 weight percent of the coating composition. The upper limit in the amount of photoconductive material present can be widely varied in accordance with usual prac- 1 percent of the coating composition to about 99 weight percent of the coating composition. A'preferred weight range for the photoconductive material in the coating composition is from about 10 weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support can vary widely. Normally, a wet coating thickness in the range of about 2.5 microns to about 300 microns is useful in the practice of the invention. Apreferred range of coating thickness is from about 50 microns to about microns before drying although such thicknesses can vary widely depending on the particular application desired for the electrophotographic element.

Suitable supporting materials for the photoconductive layers of the present invention can include any of the electrically conducting supports, for example, various conducting papers; aluminum-paper laminates; metal foils, such as aluminum foil, zinc foil, etc; metal plates such as aluminum, copper, zinc, brass, and galvanized plates; vapor deposited metal layers such as silver, nickel or aluminum on conventional film supports such as cellulose acetate, poly( ethylene terephthalate), polystyrene and the like conducting supports.

An especially useful conducting support can be prepared by coating a transparent film support material such as poly( ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin. A suitable conducting coating can be prepared from the sodium alt of a carboxy-ester lactone of a maleic anhydridevinyl acetate copolymer, cuprous iodide and the like. Suchconducting layers and methods for their optimum preparation and use are disclosed in Minsk US. Pat. No. 3,007,901, dated Nov. 7, 1961, Trevoy US. Pat. No. 3,245,833, dated Apr. 12, 1966, and Sterman et al U.S. Pat. No. 3,262,807, dated July 26, 1966.

The compositions of the present invention can be employed in photoconductive elements useful in any of the well known electrophotographic processes which require photoconductive layers. One such process is .the xerographic process. in a process of this type, an

electrophotographic element held in the dark, is given a'blanket positive or negative electrostatic charge as desired by placing it under a corona discharge to give a uniform charge to the surface of the photoconductive layer. This charge is retained by the layer owing to the substantial dark insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is thenselectively dissipated from the surface of the layer by imagewise exposure to light by means .of a conventional exposure operation such as, for example, by a contact-printing technique, or by lens projection'of an image, or reflex or birefl ex techniques and the like, to thereby form a latent electrostatic image in the photoconductive layer. Exposing the surface in this manner forms a pattern of electrostatic charge by-virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in proportion to the illuminance on a particular area.

The charge pattern produced by exposure is then de veloped or transferred to another surface and developed there, i.e., either the charged or uncharged areas rendered visible, by treatment with a medium comprising electrostatically responsive particles having optical density. The developing electrostatically responsive particles can be in the form of a dust, or powder and generally comprise a pigment in a resinous carrier called a toner. A preferred method of applying such a toner to an electrostatic image for solid area development is by the use of a magnetic brush. Methods of forming and using a magnetic brush toner applicator are known in the art. e.g., Young U.S. Pat. No. 2,786,439, Giaimo U.S. Pat. No. 2,786,440 and Young U.S. Pat. No. 2,786,441, all dated Mar. 26, 1957. Liquid developemnt of the latent electrostatic image may also be used. liquid liauiddevelopment, the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature, for example, Metcalfe et al. U.S. Pat. No. 2,907,674, dated Oct. 6, 1959. In dry developing processes, the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a low-melting resin. Heating the powderimage then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the charge image or powderimage formed on the photoconductive layer can be made to a second support such as paper which would then become the final print after developing and fusing or fusing, respectively. Techniques of the type indicated are well known in the art and have been described in the literature, such as in RCA Review, vol. (1954) pages 469-484. a The compositions of the present invention can be used in electrophotographic elements having many structural variations. For example, the photoconduc tive composition can be coated in the form of single layers or multiple layers on a suitable opaque or transparent conducting support. Likewise, the layers can be contiguous or spaced having layers of insulating material or other photoconductive material-between layers or overcoated or interposed between the photoconductive layers or sensitizing layer and the conducting layer. It is also possible to adjust the position of the support and the conducting layer by placing a photoconductor layer over a support and coating the exposed'face of the support or the exposed or overcoated face of the photoconductor with a conducting layer. Configurations differing from those contained in the examples can be useful or even preferred for the same or different application for the electrophotographicelement.

The following examples ar included for a further understanding of the invention.

EXAMPLE 1 A composition in the form of a dope consisting of the following materials is coated at a wet thickness of 150 microns on a poly(ethylene terephthalate) film support bearing a conductive layer comprising vapor deposited ened room, the surface of the photoconductive layer so prepared is charged to a potential of about +600 volts under a corona charger. The layer is then covered with a transparent sheet bearing a pattern of opaque and light-transmitting areas and exposed to the radiation from an incandescent lamp with an illumination intensity of about meter-candles for 12 seconds. The resulting electrostatic charge pattern is developed by cascading over the surface of the layer negatively charged black thermoplastic toner particles on glass bead carriers. No image is reproduced on the element containing no photoconductor; however, a good quality image is produced on the elements containing photoconductors I through VIII.

EXAMPLE 2 The elements prepared in Example 1 are each recharged under a positive corona source until the surface potential, as measured by an electrometer probe, reaches V which typically is about 600 volts. They are then exposed from behind a stepped density gray scale to a 3000K. source. The exposure causes reduction of the surface potentials of the elements under each step of the gray scale from their initial potential, V,,, to some lower potential, V, whose exact value depends on the actual amount of exposure received by the areas. The results of the measurements are plotted on a graph of surface potential V vs. log exposure for each step. The shoulder speed is the numerical expression of 104 multiplied by the reciprocal of the exposure in meter-candle-seconds required to reduce the surface potential V by 100 volts. The procedure is then repeated, using negative charging. The elementsv have speeds as thus determined as shown in Table 2 below.

Elements are prepared as in Example 1 using as the sensitizer one of 'the following Sensitizers A or B in place of Rhodamine B:

Sensitizer A' amyloxy-phenyl) thiapyrylium perchlorate Sensitizer. B 4-n-butylamino-2-(4-methoxyphenyl)benzo-(b) pyrylium perchlorate When tested according'to the procedure of Example 2, electrophotographic speeds as indicated in'Table 3 are obtained.

TABLE 3 Shoulder Speed Positive Charging Negative Charging Sensitizer Sensitizer Photoconductor None A B None A B I 0 0 63 Il 0 180 v12 0 I20 6 III 45 I00 8 63 IV 65 I10 [0 63 V 68 320 550 14 I00 20 VI 150 270 600 32 I20 62 VII 200 200 ll 80 I5 EXAMPLE 4 A first dye-containing solution is prepared by dissolving 0.03 gram of dye 2,6-diphenyl-4-(4-dimethylaminophenyl)thiapyrylium perchlorate in 7.65 grams of dichlorornethane. A second dyeand polymer-containing solution is prepared by dissolving 3.92 grams of poly(4- ,4'-isopropylidenediphenylene carbonate) (Lexan 145, General Electric Co.) in 20.0 grams of dichlorornethane which contains 0.08 gram of the above dye in solution. The second solution is subjected to shearing in a high-speed blender for a half-hour at room temperature. The two solutions are then incorportated into a photoconductor-containing coating solution to form a coating dope for each of the photoconductors listed in Table 4 below. The photoconductor-containing solution is prepared according to the following composition:

Vlll 160 90 32 Lexan 145 0.25 g. Photoconductor 0.25 g. Solution 1 4.50 g. Solution 2 7.70 g.

Each of the coating dopes thus produced is coated as in Example 1 to form photoconductive elements. Each element is then charged in turn positively and negatively and exposed as in Example 2 through a stepped density gray scale. Toe speeds obtained for both positive and negative charging at a voltage of 100 volts above zero volts are listed in Table 4.

TABLE 4 Speed Photoconductor Positive Negative None 25 21 l 71 190 ll 80 71 111 40 80 V 900 310 V1 320 250 V111 260 EXAMPLE 5 Three coating compositions in the form of a dope consisting of the following materials are prepared and coated according to the procedure of Example 1 to form an electrophotographic element:

Photoconductor 0.5 g. I

Sensitizer Sensitizer B of Example 3 0.04 g.

. Binder poly(4,4-isopropylidenebisphenyleneoxyethylene-co-ethylene isophthalate Dichloromethane 8.8 g.

Each of the elements thus produced is charged as in Example 1, and exposed to light from a xenon arc lamp which has been filtered in such a manner as to simulate as closely as possible the emission from a standard RETMA P-l6 phosphor, which has an emission peak of about 385 rim. The time required to reduce the 600- volt charged surface potential to 50 volts is measured for each of the elements prepared. A control element contains 4,4-benzylidenebis(N,N-diethyl-m-toluidine) as the photoconductor. The results of the measurements thus made are listed in Table 5.

TABLE 5 Photoconductor Time Required Control 26.3 sec. V 24.8 sec. V11 14.3 sec.

It is seen that the photoconductors of this invention give a desirable reduction in exposure time required when this mode of exposure is used.

EXAMPLE 6 Preparation of N-(p-diphenylaminobenzylidene-N'- (3-methyl-2-benzothiazal)hydrazine (Compound V) A 6.65 gram portion of 3-methyl-2- benzothiazolinone hydrazone (0.0371 mole) and an 11.2 gram portion of p-diphenylaminobenzaldehyde (0.0410 mole) are suspended in 250 ml. of absolute ethanol and heated to reflux temperature, during which time the solids dissolve. The mixture is refluxed for 16 hours and allowed to cool to room temperature, whereupon a mass of yellow crystals precipitates. After filtering and washing with cold ethanol, there result 15.0 grams of product having a melting point range of l83-185C. Recrystallization from nitromethane yields 12.3 grams of yellow cubic crystals having a melting point range of 183.5l84.SC. The other photoconductive compounds according to the invention are prepared in an analogous manner from the same hydrazone and the appropriate aldehyde. The melting point, maximum absorption (Amax) in trichlorornethane, and the extinction coefficient for each compound are summarized in Table 6 below. The extinction coefficient is represented by the expression e=Dlcl where D is the optical density of the solution, C is the concentration in moles/liter and 1 is the length (cm) of the cell holding the solution as measured along the optical path.

TABLE 6 CHCL,

Arnax 3l2 nm 353 nm 372 nm 375 11111 385 nm 389 nm 392 11111 384 nm hmax x 10 1.98 3.08 4.60 4.68 4.70 4.90 $.70 4.67

Melting Point 1 l 1.0-1 l2.5 163.0-165.0 t76.0178.0 I l38.0l40.0 1835-1845 199.5-20 l.0 220.0-222.0 2 l8.5220.0

wherein:

R R, and R are each selected from the group consisitng of an alkyl radical having one to eight carbon atoms, a phenyl radical, a naphthyl radical and a hydrogen atom;

R R R and R are each selected from the group consisting of a cyano radical, a halogen atom, an alkyl radical having one to eight carbon atoms, an alkoxy radical having one to eight carbon atoms and a disubstituted amino radical wherein the substituents are the same or different and are selected from hydrogen, lower alkyl having one to eight carbon atoms, phenyl, naphthyl and halogen; and

X is selected from the group consisting of oxygen,

sulfur, an imino group and a methylene group.

2. An electrophotographic element comprising a conductive support having thereon a layer of a photoconductive composition comprising a photoconductor, a sensitizing amount of a sensitizer for said photoconductor and an electrically insulating polymeric filmforming binder, said photoconductor having the formula:

wherein:

R R and R are each selected from the group consisting ofa hydrogen atom, a lower alkyl radical having one to about four carbon atoms, a phenyl radical and a naphthyl radical; and

Y is selected from the group consisting of oxygen,

sulfur and an imino radical.

3. An element as described in claim 2 wherein said photoconductor is selected from the group consisting of N-isopropylidene-N'-(3-methyl-2-benzothiazal)hydrazine; N-benzylidene-N'-(3-methyl-2-benzothiazal)- hydrazine; N-(p-diethylaminobezylidene)-N'-(3- methyl-Z-benzothiazal)hydrazine; N-(pdimethylaminobenzylidene )-N 3-methyl-2-benzothiazal)-hydrazine; N-(p-diphenylaminobenzylidene)- N'-(3-methyl-2-benzothiazal)hydrazine; N-(p-di-ptolylaminobenzylidene)-N'-(3-methyl 2-beniothiazal)- hydrazine; N-(p-diphenyla mino-omethoxybenzylidene)-N-(3 methyl-2-benzothiazal)- hydrazine and 'N-(4-diphenylamino-lnaphthylmethylene )-N 3-methyl-2-benzothiazal)hydrazine.

4. An electrophotographic element comprising a conductive support having thereon a layer of a photoconductive composition comprising a photoconductor, a sensitizing amount of a sensitizer for said photoconductor and an electrically insulating polymeric filmforming binder, said photoconductor having the forwherein:

' R is a lower alkyl radical having one to about four carbon atoms; and

R is selected from the group consisting of a phenyl radical and a naphthyl radical.

5. An electrophotographic element as described in claim 4 wherein said sensitizer is selected from the group consisting of pyrylium dye salts and cyanine dyes. 1

6. In anelectrophotographic process comprising the steps of l uniformly charging an electrophotographic element which comprises a conductive support having thereon a layer containing an organic photoconductor, a sensitizing amount of a sensitizer for said photoconductor and an organic film-forming polymeric binder, and (2) exposing the layer to a pattern of actinic radiation to selectively dissipate the charge in accordance with the radiation pattern, the improvement comprising using as the photoconductor an organic compound having the formula:

R R5 and R are each selected from the group consisting'of a hydrogen atom, a lower alkyl radical ving one to about four carbon atoms, a phenyl radical and a naphthyl radical; and

Y is selected from the group consisting of oxygen,

sulfur and an imino radical. 

2. An electrophotographic element comprising a conductive support having thereon a layer of a photoconductive composition comprising a photoconductor, a sensitizing amount of a sensitizer for said photoconductor and an electrically insulating polymeric film-forming binder, said photoconductor having the formula:
 3. An element as described in claim 2 wherein said photoconductor is selected from the group consisting of N-isopropylidene-N''-(3-methyl-2-benzothiazal)hydrazine; N-benzylidene-N''-(3-methyl-2-benzothiazal)hydrazine; N-(p-diethylaminobezylidene)-N''-(3-methyl-2-benzothiazal)hydrazine; N-(p-dimethylaminobenzylidene)-N''-(3-methyl-2-benzothiazal)-hydrazine; N-(p-diphenylaminobenzylidene)-N''-(3-methyl-2-benzothiazal)hydrazine; N-(p-di-p-tolylaminobenzylidene)-N''-(3-methyl-2-benzothiazal)hydrazine; N-(p-diphenylamino-o-methoxybenzylidene)-N''-(3-methyl-2 -benzothiazal)hydrAzine and N-(4-diphenylamino-1-naphthylmethylene)-N''-(3-methyl-2 -benzothiazal)hydrazine.
 4. An electrophotographic element comprising a conductive support having thereon a layer of a photoconductive composition comprising a photoconductor, a sensitizing amount of a sensitizer for said photoconductor and an electrically insulating polymeric film-forming binder, said photoconductor having the formula:
 5. An electrophotographic element as described in claim 4 wherein said sensitizer is selected from the group consisting of pyrylium dye salts and cyanine dyes.
 6. In an electrophotographic process comprising the steps of (1) uniformly charging an electrophotographic element which comprises a conductive support having thereon a layer containing an organic photoconductor, a sensitizing amount of a sensitizer for said photoconductor and an organic film-forming polymeric binder, and (2) exposing the layer to a pattern of actinic radiation to selectively dissipate the charge in accordance with the radiation pattern, the improvement comprising using as the photoconductor an organic compound having the formula: 